Study of equilibrium and nonequilibrium phase transformations temperatures of steel by thermal analysis methods

Abstract

This work deals with determining temperatures of phase transformations in steel S34MnV in a low-temperature region (below 900 A degrees C). Although S34MnV is a significant tool steel, in the literature, there are only a few works dealing with the study of the thermo-physical properties of this steel. For the study of phase transformation temperatures of steel S34MnV, a differential thermal analysis and dilatometry were used in this study. Both methods are used to determine the phase transformation temperatures of steel. Dilatometry, however, unlike differential thermal analysis, is commonly used to determine the temperature of nonequilibrium phase transformations during cooling. Temperatures of the eutectoid phase transformation (A (c1)) and temperatures of the end of the ferrite to austenite transformation (A (c3)) were obtained at heating, and temperatures of the start of the ferrite formation (A (r3)), the temperature of the start of the pearlite formation (A (r1)) and the temperature of the start of the bainite formation (B (S)) were obtained at cooling using these methods. The temperatures obtained using the both methods were compared and discussed. The original thermo-physical data on steel S34MnV were obtained under precisely defined conditions. For the complexity of the study of the steel, a metallographic analysis of samples was also conducted after thermal analysis, which enables determining the phases occurring in the final structure and their quantity. The experimentally obtained data were compared with data calculated by the software QTSteel.